1. Field of the Invention
The present invention relates to a lyophilized preparation comprising cis-1,1-cyclobutanedicarboxylate-(2R)-2-methyl-1,4-butanediamine platinum (II) (hereinafter referred to as the platinum compound) which is useful as an antitumor drug.
2. Description of the Prior Art
Generally, preparations for injection are prepared in the form of a solution, a lypophilized preparation or a powder preparation.
The platinum compound is relatively unstable in aqueous solutions so that it is highly desirable that the platinum compound be used in the form of a lyophilized preparation or a powdery preparation of its bulk drug powder, because the preparation is usually stored at room temperature over a long period of time. However, a preparation obtained merely by lyophilizing an aqueous solution of the platinum compound dissolves in water so slowly that it is necessary to conduct heating or stirring over a long period of time, when the preparation is to be redissolved. Furthermore the powder preparation dissolves more slowly than the lyophilized preparation so that redissolution is further difficult.